The broad objective of this research is to determine the biological functions of alpha-actinin and other Z-disk proteins in biological movement systems. The specific objectives are: 1) to specify the nature of the proteins constituting Z-disks in striated muscle or Z-disk analogues in nonmuscle systems; these efforts will use selective extraction, biochemical characterization, and localization of antibody binding with light and electron microscopy; 2) to ascertain the role of Z-disk proteins in assembly and disassembly of contractile systems during metabolic turnover and to learn the mechanism of this turnover; these experiments will involve studies of the Ca 2 ion-activated protease that is endogenous to muscle and that degrades Z-disks and characterization of this protease and other muscle proteases that may be involved in myofibrillar protein turnover; and 3) to determine whether alpha-actinin or other Z-disk proteins can modify actin structures in a way that alters the ability of actin to function in biological movement; these experiments will involve assays of the effect of alpha-actinin or other Z-disk proteins on the conformation of actin monomers while these monomers are aggregated in filaments.